Electric cartridge fuse having terminal caps and knife-blade contacts



Jan. 13, 1970 R. A. BELCHER ELECTRIC CARTRIDGE FUSE HAVING TERMINAL CAPS AND KNIFE-BLADE CONTACTS Filed Aug. 6, 1968 INVENTOR:

a" RICHARD A. BELCHER BY M AM ATTY.

United States Patent 3,489,979 ELECTRIC CARTRIDGE FUSE HAVING TERMINAL CAPS AND KNIFE-BLADE CONTACTS Richard A. Belcher, Hampton Falls, N.H., assignor to The Chase-Shawmut Company, Newburyport, Mass. Filed Aug. 6, 1968, Ser. No. 750,706 Int. Cl. H01h 85/04 US. Cl. 337158 2 Claims ABSTRACT OF THE DISCLOSURE In an electric cartridge fuse having blade contacts the latter are held in position by washers interposed between the rims of the casing and ferrules mounted on the ends of the casing, the aforementioned washers having such a geometrical configuration as to form abutments for locating the washers relative to the casing and to limit relative rotary movement between the washers and the blade contacts.

BACKGROUND OF INVENTION The problem of firmly maintaining the constituent parts of blade-type fuses in their respective positions is one of the most important problems in the design of electric fuses of this type. It has found many solutions in the past, but still calls for improved solutions thereof. Thepresent invention is such an improved solution of the above problem.

The present invention is an improvement of the structuredisclosed and claimed in the patent application of Kenneth W. Swain, Ser. No. 750,569 for electric cartridge fuses having blade contacts, assigned to the same assignee as the present invention.

SUMMARY OF INVENTION An electric fuse according to this invention includes a casing of insulating material and a pulverulent arcque'nching filler inside of the casing. A fusible element is embedded in the arc-quenching filler. A pair of ferrules closes the axially outer ends of the casing. Each of the ferrules has an end surface defining a slot extending across the center of the end surface. Fuses according to this invention further include a pair of blade contacts conductively interconnected by said fusible element. Each of said pair of blade contacts projects transversely through said slot defined by the end surface of each of said pair of ferrules. The longitudinal edges of each of said pair of blade contacts have a pair of transverse incisions adjacent the axially inner end of each of said pair of blade contacts. These incisions establish a point of reduced width of each of said pair of blade contacts. Fuses embodying this invention further include a pair of metal washers each arranged between one of the rims of the casing and the end surface of one of said pair of ferrules. Each of said pair of washers defines a circular center opening having a diameter substantially equal to the Width of each of said pair of blade contacts at said point of reduced width thereof. Each of said pair of washers further defines a plurality of angularly displaced openings extending radially outwardly from said center opening and defining jointly with said center opening a passage for said axially inner end of each of said pair of blade contacts. Said center opening of each of said pair of washers forms an edge entering into said pair of transverse incisions adjacent said axially inner end of one of said pair of blade contacts. This precludes movement of said pair of blade contacts in a direction longitudinally thereof relative to said pair of washers.

3,489,979 Patented Jan. 13, 1970 BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an isometric exploded view of one end of a cartridge fuse embodying the present invention;

FIG. 2 is in part a side elevation and in part a longitudinal section of the same fuse as shown in FIG. 1;

FIG. 3 is a top-plan view of the washer of the structure of FIGS. 1 and 2 and its associated parts in a relatively early state of the assembly process of the fuse, FIG. 3 being drawn on a larger scale than FIGS. 1 and 2;

FIG. 4 shows the same structure as FIG. 3 in the same fashion as FIG. 3 in a subsequent or later state of the assembly process; and

FIG. 5 shows the washer of FIG. 3 in side elevation and its associated casing in longitudinal section.

DESCRIPTION OF PREFERRED EMBODIMENT OF INVENTION In the drawings numeral 1 has been applied to indicate a tubular casing of electric insulating material such as, for instance, vulcanized fiber. Ferrules 2 of sheet metal are mounted on the axially outer ends of casing 1. The end surface 2a of each ferrule 2 is provided with a slot 2b extending across the center of the end surface. The blade contacts 3 of the fuse are conductively interconnected by a fusible element 4 in the form of a multiperforated metal ribbon. Blade contacts 3 project transversely through slots 2b in end surfaces 2a of ferrules 2. The longitudinal edges 3a of blade contacts 3 have a pair of transverse incisions 3b adjacent the axially inner ends thereof. Thus each blade contact 3 defines a point of reduced width. Reference numeral 5 has been applied to indicate a pair of circular metal washers of which each is arranged between one of the rims 1a of casing 1 and the end surface 20 of one of ferrules 2. Each of washers 5 defines a circular center opening 5a having a diameter substantially equal to the width of blade contacts 3 at the point 3!), 3b of reduced width. Each washer 5 further defines four radical openings 5b which are angularly displaced degrees. Openings 5b extend radially outwardly from circular center openings 5a. Openings 5a, 5b form jointly passages for blade contacts 3, as clearly shown in FIG. 3. In other words, the diameter of circular center opening 5a plus twice the length of each radial passage 5a exceeds the width of blade contacts 3 at the regions thereof Where their width is relatively large. Each of the pair of washers 5 has four tabs 50 which are angularly displaced 90 degrees, and bent 90 degrees out of the general plane of the respective washer 5. The four radial openings 5b defined by each of washers 5 are coextensive with four points where material of the washers is bent 90 degrees out of the general plane of washers 5 to define radial openings 5b.

During assembly of the fuse structure of FIGS. 1 and 2 washers 5 are placed on the rims 1a of casing 1. Tabs 5c then form abutments for locating washers 5 relative to casing 1. Prior to placing washers 5 on rims 1a of easing 1 the blade-contact-and-fuse-link unit 3, 4, 3 is inserted into casing 1 so that when washers 5 are placed on rims 1a of casing 1 blade contacts 5 project through openings 5a, 5b, as clearly shown in FIG. 3. Thereupon Washers 5 are pivoted from the position shown in FIG. 3 to the position shown in FIG. 4. This pivotal motion is limited by abutting engagement of the lateral surfaces of blade contacts 3 by tabs or abutments c of washers 5, as clearly shown in FIG. 4. Upon pivotal motion of washers 5 from the position shown in FIG. 3 to the position shown in FIG. 4, the edge formed by center opening 5a of each Washer 5 engages the incisions 3b in one of blade contacts 3. As a result, blade contacts 5 are precluded from moving relative to washers 5 and relative to casing 1 in a direction longitudinally of blade contact 3 and of easing 1. When unit 3, 4, 3 is firmly held in position by the operation of the two washers 5, one of the two ferrules is mounted on casing 1, thus closing the latter on one side thereof. Thereafter the fuse in the process of assembly is arranged in such a position that its end which is closed by a ferrule is at a lower level than its end which has not yet been closed by a ferrule. In that position the pulverulent arc-quenching filler 6, e.g. gypsum powder, may be filled through the openings 5a, 5b in the exposed or upper washer 5 into casing 1. When the latter is filled with arcquenching filler 6, the second or upper ferrule 2 is mounted on casing 1. Ferrules 2 are preferably press-fitted on casing 1, and the axially inner ends thereof may be crimped into casing 1 to safely preclude any movement of ferrules 2 in a direction longitudinally of casing 1. If desired, a pair of washers of asbestos fibers, or a like material (not shown) may be interposed between metal Washers 5 and ferrules Z to preclude any loss of arcquenching filler 6 through slots 2b in ferrules 2.

It will be understood that I have illustrated and described a preferred embodiment of my invention and that various alterations may be made in the details thereof without departing from the spirit and the scope of the invention as defined by the appended claims.

I claim as my invention:

1. An electric cartridge fuse including:

(a) a tubular casing of insulating material;

(b) a pulverulent arc-quenching filler inside said casing;

(c) a fusible element embedded in said arc-quenching filler;

(d) a pair of ferrules closing the axially outer ends of said casing, each of said pair of ferrules having an end surface defining a slot extending across the center of said end surfaces;

(e) a pair of blade contacts conductively interconnected by said fusible element each projecting transversely through said slot defined by said end surface of each of said pair of ferrules, the longitudinal edges of each of said pair of blade contacts having a pair of transverse incisions adjacent the axially inner end of each of said pair of blade contacts establishing a point of reduced width on each of said pair of blade contacts; and

(f) a pair of metal washers each arranged between one of the rims of said casing and said end surface of one of said pair of ferrules, each of said pair of washers defining a circular center opening having a diameter substantially equal to the width of each of said pair of blade contacts at said point of reduced width thereof, and a plurality of angularly displaced radial center opening and defining jointly with said center opening a passage for said axially inner end of each of said pair of blade contacts, said center opening of each of said pair of washers forming an edge entering into said pair of transverse incisions adjacent said axially inner end of one of said pair of blade contacts and thereby precluding movement of said pair of blade contacts in a direction longitudinally thereof relative to said pair of washers, and each of said pair of washers having a plurality of angularly displaced tabs arranged substantially at right angles to the plane defined by one said pair of washers forming abutments for locatingeach of said pair of washers during assembly operations relative to said casing, and said plurality of tabs further forming abutments for said pair of blade contacts limiting relative rotary motion between said pair of washers and said pair of blade contacts about the longitudinal axes thereof.

2. An electric fuse as specified in claim 1 wherein each of said pair of washers has four tabs being angularly displaced degrees and formed material bent 90 degrees out of the general plane of one of said pair of washers, each of said pair of washers defining four radial openings being angularly displaced 90 degrees, each of said four radial openings being coextensive with a point where material is bent 90 degrees out of the general plane of one of said pair of washers.

References Cited UNITED STATES PATENTS 1,925,060 8/1933 Stephenson 337251 X 2,166,174 7/1939 Popp 337234 2,644,872 7/1953 Laing 337-234 BERNARD A. GILHEANY, Primary Examiner H. B. GILSON, Assistant Examiner US. Cl. X.R. 337-231 

